Time-based Media:Understanding Guideline 1.2

Intent of Guideline 1.2

The purpose of this guideline is to provide access to synchronized media. Synchronized media is defined in the glossary as:

synchronized media

audio or video synchronized with another
format for presenting information and/or with time-based interactive components, unless the media is a media alternative for text that is clearly labeled as such

Note that an audio file accompanied by interaction is covered here, as is a video-only file that involves interaction. These are covered because interaction must take place at a particular time. Having a text transcript that said, "for more information, click now," would not be very helpful since the reader would have no idea when the audio said, "now." As a result, synchronized captions would be needed.

Sometimes, there is so much dialogue that audio description cannot fit into existing pauses in the dialogue. The option at Level A to provide an alternative for time-based media instead of audio description for synchronized media would allow access to all of the information in the synchronized media. This option also allows access to the visual information in non-visual form when audio description is not provided for some other reason.

For synchronized media that includes interaction, interactive elements (for example links) could be embedded in the alternative for time-based media.

This guideline also includes (at Level AAA) sign language interpretation for synchronized media as well as an approach called extended audio description. In extended audio description, the video is frozen periodically to allow more audio description to take place than is possible in the existing pauses in the dialogue. This is a case where higher-level Success Criteria build upon the requirements of lower-level Success Criterion with the intention of having cumulative, progressively stronger, requirements.

Advisory Techniques for Guideline 1.2 (not success criteria specific)

Specific techniques for meeting each Success Criterion for this guideline are listed in the understanding sections for each Success Criterion (listed below). If there are techniques, however, for addressing this guideline that do not fall under any of the success criteria, they are listed here. These techniques are not required or sufficient for meeting any success criteria, but can make certain types of Web content more accessible to more people.

All advisory techniques for this guideline relate to specific success criteria and are listed below.